1. Field of the Invention
The invention relates to a method for removing injection-molded items from an injection-molding machine by a robot. The injection-molding machine and the robot are each provided with a separate drive, and each drive can be acted on by a separate open- and closed-loop control unit that can be programmed separately. The injection-molding machine is equipped with at least one signaling device for detecting a position of the mold.
2. Discussion of Background Information
It is in the nature of things that the production time for the production of injection-molded items should be shortened. One approach for reducing the cycle time was to equip the removal axes of the robots with massive drives, power transmissions and base structures, in order to achieve high speeds or accelerations. In pursuance of this way, it showed that these fast robots never reach their theoretically calculated speeds at relatively short axis paths, as they already have to decelerate again after a short acceleration phase in order to reach the target position. To compensate these conditions, the acceleration values must be set to a very high level, which results in a massive and expensive design.
There are also factors aside from the robot that influence the unproductive time, such as the speed of the ejector, the opening time of the machine, signal transmission or the like.
Thus, a method and apparatus for controlling the movements of an injection-mold and a handling device are known from DE 40 03 372 C1. In order to control the opening and closing movement of an injection-mold and the feed and extraction movement of a handling device for the removal of the molding in a concerted manner, the opening movement of the mold and/or the extraction movement of the handling device is detected in relation to position and speed. The disadvantage thereby is the higher cost in hardware parts.
In addition, a method for removal of injection-molded items from an injection-molding machine using a handling robot is known from DE 41 10 948 C2, wherein both the injection-molding machine and the handling robot are each provided with a separate drive that can be acted on by a separate open- and closed-loop control unit that can be programmed separately. At least the injection-molding machine is equipped with at least one displacement sensor to control the process. Also in this case, the high cost of components is a disadvantage.
Furthermore, a method for demolding a molded part as well as a device for carrying out the process is known from WO 91/11313. According to the method, the molded part is moved to an intermediate position in a first partial movement at low speed, then to the final position in a second partial movement at higher speed. For this purpose, the injection-mold has pressure operated stops which act on the front face of an ejection plate. A high component cost is also required for this design.
Finally, a method for operating a handling unit on a plastics processing machine is also known from DE 197 16 777 C2. The disadvantage of this method, however, is movement interruptions in the movement of the robot in borderline cases when the permissible areas are left marginally.